Problem 44958. Crop an Image
A grayscale image is represented as a matrix in MATLAB. Each matrix element represents a pixel in the image. An element value represents the intensity of the pixel at that location.
Create a cropped image matrix Icrop using inputs given in the following order:
 I  Grayscale input image
 Rmin  Lowest row number to retain
 Cmin  Lowest column number to retain
 Rpix  Number of pixels along rows to retain
 Cpix  Number of pixels along columns to retain
For example, if your image was:
I = [1 2 3 4 5 6 7 8]
And you called crop_image with inputs
Icrop = crop_image(I, 2, 2, 1, 3)
The output Icrop should be
[6 7 8]
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Problem Comments

24 Comments
you should mention which is which in this matrix Icrop = crop_image(I, 2, 2, 1, 3)
Thank you Payam. I assume you meant specifying the order of the inputs explicitly. I have updated the description to make it clearer.
Good problem!
Can someone help me to solve this question? I did not learn image processing. So I tried to solve this question assuming that the pixels either have a value of 1 or 0. I am a beginner. This is my second day into coding. I would really love some help. This is my code:
[Ix,Iy]=size(I);
for n = 1:Ix %for Rmin
if I(n,:)==0
n = n + 1;
else n = n;
break
end
end
Rmin = n
for m = 1:Iy %for Cmin
if I(:,m)==0
m = m + 1;
else m = m;
break
end
end
Cmin = m
for o = Rmin:Ix %for Rmax
if I(o,Cmin) == 1
o = o+1;
elseif I(o,Cmin) == 0
o = o  1;
break;
end
end
Rmax = o
for p = Cmin:Iy %for Cmax
if I(Rmin,p) == 1
p = p+1;
elseif I(Rmin,p) == 0
p = p  1;
break;
end
end
Cmax = p
Rpix = Rmax  Rmin + 1
Cpix = Cmax  Cmin + 1
Hint please?
Hint 1: You need not know or use anything about the value of pixels in this image.
Hint 2: All you have to do is get a subset of a matrix in MATLAB (the matrix, in this case, represents an image).
The problem generates all the input values, so what is the reason I get a "Out of memory. The likely cause is an infinite recursion within the program." error when I simply input:
Icrop = crop_image(I, Rmin, Cmin, Rpix, Cpix)
I suggest to improve problem's statement.
I found I had to check my indices and subtract one.
I saw that image cropping function is frequently used in digital image processing
yea improve the statement
this is good concept for image processing
Difficult problem!
It took me time to do this
Very good conceptual problem about image.
(Rmin,Cmin) is the (x,y) coordinate of the image's lefttop point, and Rpix*Cpix is the size of the rectangle image.
interesting problem
Good problem
Why doesn't this work?
Icrop = I(Rmin:Rmin+Rpix, Cmin:Cmin+Cpix)
I am a beginner, but this seems correct if I'm understanding the problem statement. Maybe I'm not..
@Jeremy, your approach is correct. but your formula needs a slight change. Try your formula on the given example and you'll see
I really don't get neither the example given nor the question asked. Could someone explain it?
Rmin  start keeping image from row
Cmin  start keeping image from column
Rpix  the number of rows to keep starting from Rmin
Cpix  the number of columns to keep starting from Cmin
good one..
Problem is interesting to solve.
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